Optical waveguides – With disengagable mechanical connector – Optical fiber/optical fiber cable termination structure
Reexamination Certificate
2000-06-07
2002-01-22
Lee, John D. (Department: 2874)
Optical waveguides
With disengagable mechanical connector
Optical fiber/optical fiber cable termination structure
C385S060000, C385S071000, C385S083000
Reexamination Certificate
active
06340247
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an optical connector ferrule serving as a component of an optical connector and used for connection of a fiber optic ribbon cable, a mold for molding a ferrule, a method of manufacturing an optical connector ferrule, and a method of inspecting an optical connector ferrule.
BACKGROUND ART
FIGS. 18 and 19
show a pair of optical connectors Cg called MT connectors. Each optical connector Cg has an optical connector ferrule
81
B and fiber optic ribbon cable
82
. The ferrule
81
B is made of a molding resin and mounted on an end of the fiber optic ribbon cable
82
. The ferrule
81
B has a pair of guide holes
92
and fiber positioning holes
93
. The openings of the pair of guide holes
92
and fiber positioning holes
93
appear on an end face
91
opposing the optical connector Cg to be connected. The respective optical fibers, contained in the fiber optic ribbon cable
82
, are arranged in the fiber positioning hole
93
. The pair of guide holes
92
extend through the ferrule
81
B from the one end face
91
to the other end face opposing the one end face. A stainless guide pin
83
is inserted into each of the pair of holes
92
. As shown in
FIG. 19
, the guide pins are inserted into the guide holes
92
and positioned therein, whereby the pair of optical connectors Cg are connected to each other. This connection is held using a clamp spring
85
. JIS C5981 provides detailed description of this optical connector type.
DISCLOSURE OF THE INVENTION
The present inventor found the following problems in the course of studying these optical connectors.
Each optical connector Cg has the guide pins
83
and resin ferrule
81
B. Since the thermal expansion coefficient of the guide pins
83
is different from that of the ferrule
81
B, temperature change causes stresses between the guide pins
83
and guide holes
92
. Owing to these stresses, the positions of the optical fibers held in one optical connector Cg may shift from the positions of the optical fibers held in the other optical connector Cg. The inventor thinks that such shifts increase connection loss between these connectors.
Japanese Patent Laid-Open No. 6-138344 discloses a technique associated with an optical connector. This optical connector includes two different types of guide members in a resin ferrule. One of these types of guide member includes fiber fixing grooves for fixing optical fibers and guide projections. The other of these types of guide members includes fiber fixing grooves for fixing optical fibers and guiding depressions. Each of guide members is integrally formed with an Invar alloy. Each fiber fixing groove has a rectangular cross-section with a bottom and two sides. Each guide projection has a rectangular cross-section. The guiding depressions guide the guide projections inserted thereto with the two opposite sides of the guiding depressions.
The inventor paid attention to the following point in the course of studying the optical connector disclosed in the above reference.
Since each fiber fixing groove has a bottom surface and two sides, the fixed optical fiber is surrounded by three surfaces of the Invar alloy and one surface made of material different from Invar Alloy. The guiding depressions guide the inserted guide projections by the two opposing side surfaces thereof. For this reason, each guide projection is surrounded by the two surfaces made of one material and the two surfaces made of another material. The optical fibers, guide projections, and guiding depression is accommodated in the connector are surrounded in a plurality of kinds of materials. With temperature changes, various thermal stresses, dependent on the materials they contact, are applied to these accommodated components. The inventor thinks that the thermal stresses may interfere with higher-speed transmission.
It is, therefore, an object of the present invention to provide an optical connector ferrule that allows the formation of an optical connector having good transmission performance, a mold available for the formation of the ferrule, a method of manufacturing the ferrule, and a method of inspecting the ferrule.
An optical connector ferrule according to the present invention comprises one or more optical fiber accommodating holes, a mating surface, a first guide projection, and a guide engaging portion. Each of the optical fiber accommodating holes has an inner surface and one end portion. The inner surface is made of resin and extends along a predetermined axis. The inner surface are provided so as to face the side surface of the optical fiber when an optical fiber is inserted into one of the optical fiber accommodating holes. The openings of the optical fiber accommodating holes appear in the mating surface. The first guide projection and guide engaging portion continuously extend from the mating surface along the predetermined axis so as to be allowed to position the connector with another connector to be connected. The optical fiber accommodating holes, mating surface, first guide projection, and guide engaging portion are made of one piece molded resin.
Since the optical fiber accommodating holes, first guide projection, and guide engaging portion are formed into an integral component with resin, there is no need to use any positioning components made of different materials, e.g., metal guide pins. Since no additional positioning components are required, stresses due to temperature changes do not concentrate on any specific part of the ferrule. In addition, since the stresses are dispersed throughout the ferrule through the integral resin, deformation due to such stresses does not occur in only specific part of the ferrule. This reduces the positional offsets of the optical fiber accommodating holes due to temperature changes. This improves the positioning precision between the ferrules of a pair of connectors to be connected to each other.
In the ferrule according to the present invention, each optical fiber accommodating hole can be formed between the first guide projection and guide engaging portion. This facilitates inspecting the positions of the optical fiber accommodating holes. In addition, since the guide projection and guide engaging portion are disposed so as to sandwich the optical fiber accommodating holes, this can compensate on positional offset due to the deformation of the guide projection and guide engaging portion. The guide engaging portion may be a second guide projection or guide hole.
In the ferrule according to the present invention, the guide engaging portion can include a second guide projection, made of resin, continuously extending from the mating surface along the predetermined axis. Both the first and second guide projections, made of the same material, continuously extend from the mating surface along the predetermined axis. This further improves the positioning precision of optical fiber accommodating holes which is affected by temperature changes.
In the ferrule according to the present invention, each of the first and second guide projections has a cross-sectional area of the proximal portion gradually increasing toward the mating surface along the predetermined axis. As the cross-sectional area increases, the mechanical strength is enhanced in the proximal portion of each guide projection on which forces tend to concentrate in the attachment/detachment of the ferrule.
In the ferrule according to the present invention, each of the first and second guide projections has a circular cross-section taken on a plane intersecting the predetermined axis. The high symmetry of the cross-sectional shape is advantageous to keep the linearity of the projection even when the guide projection is made of resin. This further improves the positioning precision of the optical fiber accommodating holes.
In the ferrule according to the present invention, the guide engaging portion can include a guide hole with an inner surface made of resin extending along the predetermined axis, and a bottom surface made of resin.
Since the ferrule has a guide projection
Kakii Toshiaki
Katsura Hiroshi
Sakurai Wataru
Shibata Masahiro
Doan Jennifer
Lee John D.
McDermott & Will & Emery
Sumitomo Electric Industries Ltd.
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